JPH102810A - Stress measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stress measuring device for accurately and stably measuring the amount of the stress caused in an object or its temporal variation in a simple constitution. SOLUTION: A magnetostrictive body 2 causing change of permeability according to a stress is fixed to an object 1 to which load F is applied and DC magnetic field is applied to the magnetostrictive body 2 by a magnet 3. In this condition, an electromotive signal according to temporally variation of flux of the magnetostrictive body 2 when the load F is applied (time differential value of the magnetic flux) is produced by a coil. The signal produced by the coil 4 represents temporally variation of stress (time differential value of the stress) caused in the object 1 and the temporally variation of the stress is directly measured by the signal of the coil 4. The signal of the coil 4 is integrated by an integrator 11 and amount of the stress is measured by the integrated signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the magnitude of a stress generated on an object to which a load acts, or an amount of a temporal change thereof.

[0002]

2. Description of the Related Art In a load test, an impact test, a collision test, and the like of various objects such as a vehicle, the magnitude of a stress generated in the object due to a load applied to the object, or a temporal change amount thereof. It is common practice to measure (time differential value of the magnitude of stress). In the case of a mechanical device such as an electronically controlled suspension of an automobile, when the operation of the mechanical device is controlled in accordance with a load acting on a specific portion (for example, a connection portion between a suspension damper and a vehicle body), It is necessary to measure the magnitude of the stress generated by the load on the object at the specific site, or the amount of temporal change thereof.

[0003] As an apparatus for performing such stress measurement, conventionally, for example, a strain gauge is fixed to an object or a strain-generating body integrated with the object, and based on an output signal of the strain gauge, the object is measured. It is generally known to measure the generated stress. In this case, the strain gauge generates a signal of a level corresponding to the magnitude of the stress generated in the object, and the magnitude of the stress is measured based on the signal level. Furthermore, when measuring the temporal change of the stress generated in the object, by differentiating the output signal of the strain gauge,
Signal data indicating the temporal change of the stress is generated, whereby the temporal change of the stress is measured.

However, in such a conventional stress measuring device, the strain gauge is generally susceptible to noise, temperature change, and the like, and it is difficult to perform stable and accurate stress measurement. I was

[0005] In particular, when measuring the temporal change of stress generated in an object, the output signal of the strain gauge is differentiated. In this case, a noise component included in the output signal of the strain gauge is used. Is generally higher in frequency than the signal component corresponding to the magnitude of the stress, so that in the signal data obtained by differentiating the signal component, the power of the noise component (which is proportional to the frequency of the noise component) increases. . Therefore, it has become even more difficult to stably and accurately measure the temporal change in stress from such signal data.

[0006]

SUMMARY OF THE INVENTION In view of the above background, the present invention provides a stress measuring apparatus capable of accurately and stably measuring the magnitude of a stress generated in an object or its temporal change with a simple configuration. The purpose is to provide.

[0007]

As a result of various studies, the inventors of the present invention have found that the above-mentioned object can be achieved by using a magnetostrictive body which changes the magnetic permeability according to stress. Was found.

That is, in a magnetostrictive body, when the magnetic flux passing through the magnetostrictive body is φ and the stress generated in the magnetostrictive body is σ, the temporal change amount (dφ / dt) of the magnetic flux φ and the temporal change of the stress σ The following relational expression (1) holds between the change amount (dσ / dt).

[0009]

(Equation 1)

In the equation (1), B is the magnetic flux density (密度 φ) in the magnetostrictive body, H is the magnetic field applied to the magnetostrictive body, μ
Is the magnetic permeability of the magnetostrictive body.

In this case, since dμ / dσ is substantially constant in the magnetostrictive body, if a magnetic field H applied to the magnetostrictive body is a DC magnetic field (≠ 0) whose magnitude and direction do not change with time, the following equation is obtained. H · dμ / dσ on the right side of (1) is a constant (≠
0), and therefore the amount of change in magnetic flux φ over time (dφ / d
t) and the temporal change amount (dσ / dt) of the stress σ have a proportional relationship as shown in the following equation (2).

[0012]

(Equation 2)

Therefore, if the temporal variation (dφ / dt) of the magnetic flux φ is detected in a state where a DC magnetic field is applied to the magnetostrictive body, the temporal variation (dσ / d) of the stress σ is immediately detected.
t) can be measured.

Further, the temporal change amount (d
By integrating (φ / dt), the integrated value is proportional to the magnitude of the stress σ as shown in the following equation (3), so that the magnitude of the stress σ can be measured from the integrated value.

[0015]

(Equation 3)

The amount of change in magnetic flux φ over time (dφ / dt)
Can be detected according to Faraday and Lenz's law by generating an electromotive force signal proportional to the time variation (dφ / dt) by a coil interlinking with the magnetic flux φ.

Based on the above findings, the first aspect of the stress measuring device of the present invention measures the temporal change of the stress generated in the object to which a load is applied in order to achieve the above object. A stress measuring device, wherein the magnetostrictive body is fixed to the object and causes a change in magnetic permeability according to a stress generated in the object; a DC magnetic field applying unit for applying a DC magnetic field to the magnetostrictive body; Magnetic flux change detecting means for generating a signal corresponding to a temporal change amount of a magnetic flux of the magnetostrictive body due to a change in magnetic permeability of the magnetostrictive body due to a stress generated in the object in a state where the magnetic flux change is applied. And measuring the temporal change of the stress generated in the object based on the signal as a signal indicating the temporal change of the stress generated in the object.

Alternatively, a second aspect of the stress measuring device of the present invention is a stress measuring device for measuring a temporal change of a stress generated in an object to which a load is applied in order to achieve the above object. The object comprises a magnetostrictive body which causes a change in magnetic permeability according to the stress generated therein, a DC magnetic field applying means for applying a DC magnetic field to the object, and a DC magnetic field applying means for applying the DC magnetic field to the object in a state where the DC magnetic field is applied. A magnetic flux change detecting means for generating a signal corresponding to a temporal change amount of a magnetic flux of the object due to a change in magnetic permeability of the object due to a stress, wherein the signal generated by the magnetic flux change detecting means And measuring the temporal change of the stress generated in the object based on the signal as an indicator of the temporal change of the generated stress.

According to the first or second aspect of the present invention, a state in which a DC magnetic field is applied by the DC magnetic field applying means to the magnetostrictive body fixed to the object or the object made of the magnetostrictive body. Then, when a load is applied to the target object, the stress generated in the target object changes the magnetic permeability of the magnetostrictive body fixed to the target object or the target made of the magnetostrictive body, and the magnetostrictive body or the target object is moved. The passing magnetic flux changes. Then, a signal corresponding to the temporal change amount of the magnetic flux is generated by the magnetic flux change detecting means. At this time, the temporal change amount of the magnetic flux in the magnetostrictive body fixed to the target object or the target object consisting of the magnetostrictive body is, as apparent from the above description, substantially proportional to the temporal change amount of the stress generated in the target object. Therefore, the temporal change of the stress generated in the object is directly measured from the signal generated by the magnetic flux change detecting means.

In this case, the DC magnetic field applying means for applying a DC magnetic field to the magnetostrictive body fixed to the object or the object formed of the magnetostrictive body can be simply constituted by, for example, a magnet or a coil to which a DC current is applied. .

Further, the magnetic flux change detecting means for generating a signal corresponding to the temporal change amount of the magnetic flux is, for example, a magnetostrictive body fixed to the target or a coil interlinked with the magnetic flux passing through the target consisting of the magnetostrictive body. Can be configured.

Therefore, according to the first or second aspect of the present invention, the signal generated by the magnetic flux change detecting means is not differentiated, and the time of the stress directly generated on the object from the signal is obtained. Since the target change amount can be measured, the stress temporal change amount can be accurately and stably measured with a simple configuration.

Next, a third aspect of the stress measuring device according to the present invention is a stress measuring device for measuring a magnitude of a stress generated on an object to which a load is applied in order to achieve the above object. A magnetostrictive body fixed to the object and causing a change in magnetic permeability according to a stress generated in the object, a DC magnetic field applying means for applying a DC magnetic field to the magnetostrictive body, and the object in a state where the DC magnetic field is applied. A magnetic flux change detecting means for generating a signal corresponding to a temporal change amount of a magnetic flux of the magnetostrictive body due to a change in magnetic permeability of the magnetostrictive body due to a stress generated in an object; and a signal generated by the magnetic flux change detecting means for the object. Integrating means for integrating a temporal change amount of the stress generated in the object indicated by the signal as an indicator of a temporal change amount of the stress generated in the object, wherein the integration value obtained by the integrating means is Of the stress generated in the object And measuring the of the tree.

Alternatively, a fourth aspect of the stress measuring device of the present invention is a stress measuring device for measuring a magnitude of a stress generated on an object to which a load is applied in order to achieve the above object, A DC magnetic field applying means for applying a DC magnetic field to the object, the DC object being formed of a magnetostrictive body which changes a magnetic permeability according to a stress generated in the object, and a stress generated in the object in a state where the DC magnetic field is applied; A magnetic flux change detecting means for generating a signal corresponding to a temporal change amount of a magnetic flux of the object due to a change in magnetic permeability of the object; and a stress generated in the object by the signal generated by the magnetic flux change detecting means. Integrating means for integrating the temporal change of the stress generated in the object indicated by the signal as indicating the temporal change of,
The magnitude of the stress generated in the object is measured based on the integrated value obtained by the integrating means.

According to the third or fourth aspect of the present invention, similarly to the first or second aspect, when a load is applied to an object and a stress is generated, the magnetic flux change detecting means is used. A signal is generated in accordance with the temporal change amount of the magnetic flux of the magnetostrictive body fixed to the target or the target made of the magnetostrictive body, and this signal indicates the temporal change of the stress generated in the target. . Therefore, an integrated value obtained by componentizing the temporal change amount of the stress indicated by the signal by the integrating means indicates the magnitude of the stress, and the magnitude of the stress is measured based on the integrated value. In this case, even if the signal generated by the magnetic flux change detecting means includes a high-frequency noise component, the power of the noise component is reduced in inverse proportion to the frequency by being integrated by the integrating means. Therefore, the noise component is reduced in the integrated value obtained by the integrating means.

As in the first or second embodiment, the DC magnetic field applying means can be easily constituted by, for example, a magnet or a coil energized with a DC current.
Further, the magnetic flux change detecting means can be simply constituted by, for example, a magnetostrictive body fixed to the object or a coil interlinked with a magnetic flux passing through the object made of the magnetostrictive body.

Therefore, according to the third or fourth aspect of the present invention, an object is generated in an object by an integral value obtained by integrating a temporal change amount of a stress indicated by a signal generated by a magnetic flux change detecting means. By measuring the magnitude of the stress, the magnitude of the stress can be accurately and stably measured with a simple configuration.

In each aspect of the present invention, the DC magnetic field applying means can be constituted by a magnet or a coil to which a DC current is applied as described above, but the DC magnetic field applying means has a magnetic polarity in advance. It may be constituted by the magnetized object itself, in other words, the object itself may be magnetized.

By doing so, a dedicated magnet or coil for constituting the DC magnetic field applying means is not required, and the configuration of the stress measuring device can be further simplified.

In each aspect of the present invention, a magnetic shield member is provided around the magnetostrictive body fixed to the object, the DC magnetic field applying means and the magnetic flux change detecting means, or
It is preferable to provide a magnetic shield member around the object made of the magnetostrictive body, the DC magnetic field applying means, and the magnetic flux change detecting means.

By doing so, it is possible to eliminate the influence of the external magnetic field, and it is possible to improve the measurement accuracy of the temporal change amount of the stress generated in the object and the magnitude of the stress.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a system configuration diagram showing a part of the stress measuring device of the present embodiment in a perspective view. Note that this embodiment corresponds to the first and third aspects of the present invention.

In FIG. 1, the stress measuring device according to the present embodiment measures the magnitude of a stress generated in a rod-shaped object 1 to which a compressive or tensile load F is applied in a longitudinal direction and a temporal change thereof (a magnitude of a stress). For example, pure iron or an iron-based amorphous alloy that is integrally fixed to the outer peripheral surface of the object 1 at approximately the center of the object 1 in the longitudinal direction with an adhesive or the like. , A magnet 3 as a DC magnetic field applying means fixed to the outer periphery of the lower part of the object 1, and a magnetic flux arranged so as to surround the object 1 at the location of the magnetostrictive body 2. A coil 4 as a change detecting means, and a measuring circuit 5 for processing an output signal of the coil 4 are provided, and the magnetostrictive body 2, the magnet 3, and the periphery of the coil 4 are substantially magnetic shield members made of, for example, pure iron. Covered by a tubular cover body 6 There. The magnet 3 is formed of, for example, a ferrite magnet or the like, and generates a DC magnetic field H (a magnetic field having a constant magnitude and direction) along the longitudinal direction of the object 1 as shown in FIG. .

The cover 6 has the magnetostrictive body 2, the magnet 3, and the coil 4 with the upper end and the lower end of the object 1 protruding from holes 6 a, 6 b formed in the upper and lower surfaces, respectively. The upper surface and the lower surface cover the periphery and the hole 6
It is fixed to the outer periphery of the object 1 at the points a and 6b. The coil 4 is fixed to the inner peripheral surface of the cover 6. The magnet 3 may be fixed to the inner peripheral surface of the cover 6.

The measuring circuit 5 is composed of the coil 4 and the cover 6
, A low-pass filter 7 for inputting an output signal of the coil 4 via a lead wire 4a led out, an amplifier 8 for amplifying the output of the low-pass filter 7, and an amplifier 8
Splitter 9 that bisects the output of
And the first output of the splitter 9 is directly used as the first output.
Output from the output terminal 10 to the outside and splitter 9
A signal obtained by integrating the other output from the integrator 11 (integrating means) is output from the second output terminal 12 to the outside.

Next, the operation of the stress measuring device will be described.

When a load causing a temporal change in the longitudinal direction is applied to the object 1, a stress corresponding to the load is generated in the object 1 and the magnetostrictive body 2 fixed to the object 1.
The magnetic permeability of the magnetostrictive body 2 changes according to the stress. For this reason, the magnetic flux (≒ μ · HS · s, where μ is the magnetic permeability of the magnetostrictive body 2 and S is the cross-sectional area of the magnetostrictive body 2) generated by the DC magnetic field H applied from the magnet 3 is temporal. Make a change. As a result, the magnetic flux penetrating through the coil 4 (the magnetic flux linking with the coil 4) changes with time, so that the coil 4
Generates an electromotive force signal (Δdφ / dt, where φ is a magnetic flux) at a level proportional to the temporal change of the magnetic flux of the magnetostrictive body 2 (the time differential value of the magnetic flux) according to Faraday and Lenz's law. In this case, as shown in the above equation (2), the temporal change amount of the magnetic flux of the magnetostrictive body 2 is the temporal change amount of the stress generated in the integrated object 1 of the magnetostrictive body 2 (the time of the stress). (Differential value), the level of the electromotive force signal generated in the coil 4 as described above is proportional to the temporal change amount of the stress generated in the object 1.

The electromotive force signal generated in the coil 4 in this manner is supplied to the low-pass filter 7 in the measuring circuit 5.
After the high-frequency noise component is almost removed, the signal is amplified by the amplifier 8 and output to the first output terminal 10 via the splitter 9. Further, the electromotive force signal of the coil 4 amplified by the amplifier 8 is input to the integrator 11 via the splitter 9, and a signal integrated by the integrator 11 is output to the second output terminal 12.

In this case, the signal obtained at the first output terminal 10 is basically a signal obtained by amplifying the electromotive force signal generated in the coil 4 by the amplifier 8 as it is, and the level of the electromotive force signal is As described above, the level of the signal generated at the first output terminal 10 is proportional to the temporal change amount of the stress generated in the object 1, and the temporal change amount of the stress generated in the object 1 It will be shown. Therefore, it is possible to directly measure the temporal change amount of the stress generated in the object 1 by the signal obtained at the first output terminal 10.

Since the signal obtained at the first output terminal 10 is obtained without differentiating the electromotive force signal of the coil 4, the high-frequency noise component that cannot be completely removed by the low-pass filter 7 is obtained. Is not included in the first output terminal 10
By using the obtained signal, the temporal change of the stress generated in the object 1 can be measured relatively accurately and stably.

The signal obtained at the second output terminal 12 is obtained by integrating the electromotive force signal generated in the coil 4 by the integrator 11 in proportion to the temporal change of the stress generated in the object 1. Therefore, the signal level of the second output terminal 12 is proportional to the magnitude of the stress generated in the object 1 (see the above equation (3)). Therefore, the magnitude of the stress generated in the object 1 can be measured based on the signal level obtained at the second output terminal 12. In this case, by integrating the electromotive force signal generated in the coil 4 by the integrator 11, the power of the high-frequency noise component that cannot be completely removed by the low-pass filter 7 decreases in inverse proportion to the frequency. The magnitude of the stress generated in the object 1 by the signal obtained at the second output terminal 12 can be accurately and stably measured.

The magnetostrictive body 2, magnet 3, and coil 4 for generating a signal indicating a temporal change amount of the stress generated in the object 1 as described above have a cover around which a magnetic shield member is provided. Since they are covered by the pair 6, the external magnetic field is prevented from acting on them. Therefore, the electromotive force signal generated by the coil 4 correctly indicates the temporal change amount of the stress generated in the object 1, and the temporal change amount and the magnitude of the stress can be accurately measured.

Next, a second embodiment of the stress measuring device of the present invention will be described with reference to FIG. FIG. 2 is a system configuration diagram showing a part of the stress measuring device of the present embodiment in a perspective view. In the present embodiment, only a part of the first embodiment is changed. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and the description is omitted.

Referring to FIG. 2, in the present embodiment, as a DC magnetic field applying means for applying a DC magnetic field H to a magnetostrictive body 2 fixed to an object 1, instead of the magnet 3 shown in FIG. A coil 13 extrapolated below the object 1 in the cover body 6 is provided, and a DC current is applied to the coil 13 from a DC power supply 14 provided outside the cover body 6 via a resistor 15. As in the case of the magnet 3, a DC magnetic field H is generated. The other configuration is completely the same as that of the first embodiment.

In the stress measuring device of this embodiment, only the configuration of the DC magnetic field applying means is different from that of the first embodiment. When a load F is applied to the object 1, a temporal change amount of the stress generated in the object 1 is measured relatively accurately and stably by a signal obtained at the first output terminal 10 of the measurement circuit 5. In addition, the magnitude of the stress can be accurately measured by a signal obtained at the second output terminal 12.

In the first and second embodiments, the DC magnetic field applying means is constituted by the magnet 3 and the coil 13. However, when the object 1 is made of a magnetic material, it is magnetized in advance. It may be magnetized, and the DC magnetic field H may be applied to the magnetostrictive body 2 by the object 1 itself. In this case, the magnet 3 and the coil 13 become unnecessary.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a system configuration diagram showing a part of the stress measuring device of the present embodiment in a perspective view. Although this embodiment corresponds to the second and fourth aspects of the present invention, since the basic configuration is the same as that of the first embodiment, the same components are denoted by the same reference numerals. And the detailed description is omitted.

Referring to FIG. 3, in the present embodiment, bar-shaped object 16 to which a compressive or tensile load F is applied in the longitudinal direction is made of a magnetostrictive body such as carbon steel. Then, similarly to the first embodiment, the magnet 3 (DC magnetic field applying means) for applying the DC magnetic field H to the object 16 is fixed to the outer periphery of the lower part of the object 16,
A coil 4 serving as a magnetic flux change detecting means is arranged around a substantially central portion in the longitudinal direction of the object 16, and a measuring circuit 5 is connected to the coil 4. Further, similarly to the first embodiment, a cover 6 is provided to cover the periphery of the magnet 3 and the coil 4 and an intermediate portion of the object 6.
The upper and lower ends of the object 6 protrude from the upper and lower surfaces of the object 6.

Therefore, the stress measuring device of the present embodiment has the same structure as that of the first embodiment, except that the object 1 is made of a magnetostrictive body and the magnetostrictive body 2 is removed.

In the stress measuring device according to the present embodiment, when a load causing a temporal change in the longitudinal direction is applied to the object 16, a stress corresponding to the load is generated in the object 16, and at this time, The magnetic permeability of the object 16 changes according to the stress. Therefore, the magnetic flux (≒ μ ′ · H ·) generated in the object 16 by the DC magnetic field H applied from the magnet 3
S ′, where μ ′ is the magnetic permeability of the object 16 and S ′ is the cross-sectional area of the object 16). As a result, the magnetic flux penetrating through the coil 4 (the magnetic flux interlinking with the coil 4) changes with time, just like the first embodiment, so that the magnetic flux of the object 16 is applied to the coil 4. Of the coil 4 is generated, and the level of the electromotive force signal of the coil 4 is proportional to the temporal change of the stress generated in the object 1. It will be.

Therefore, just like in the first embodiment, when a load F is applied to the object 1, the signal obtained at the first output terminal 10 of the measuring circuit 5 causes the object 1 to receive a signal. The temporal change of the generated stress can be measured relatively accurately and stably, and the magnitude of the stress can be measured accurately by the signal obtained at the second output terminal 12.

In this embodiment, the magnet 3 is used as the DC magnetic field applying means. However, the DC magnetic field applying means may be constituted by using a coil as in the second embodiment.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 is a system configuration diagram showing a part of the stress measurement device of the present embodiment in a perspective view. In the present embodiment, only a part of the third embodiment is changed. Therefore, the same components as those of the third embodiment are denoted by the same reference numerals, and the description is omitted.

Referring to FIG. 4, in the stress measuring device according to the present embodiment, the object 16 made of the magnetostrictive body of the third embodiment is formed such that its upper end is an N pole and its lower end is an S pole. Is magnetized in advance, and the magnet 3 provided in the third embodiment is removed. That is, in the stress measuring device of the present embodiment, the object 16 is magnetized (magnetized) in advance, and the object 16 itself is replaced with the magnet 3 of the third embodiment. It is configured as DC magnetic field applying means for applying a DC magnetic field H to the object 16. The other configuration is completely the same as that of the third embodiment.

The stress measuring device of this embodiment differs from that of the third embodiment only in that a DC magnetic field H is applied to the object 16 by the object 16 itself. In the same manner as in the third embodiment and the first embodiment, when a load F is applied to the object 1, the signal obtained at the first output terminal 10 of the measurement circuit 5 The temporal change amount of the stress generated in the object 1 can be measured relatively accurately and stably, and the magnitude of the stress can be measured accurately by the signal obtained at the second output terminal 12.

Furthermore, in this embodiment, since a magnet or a coil for applying a DC magnetic field to the object 16 is not required, the configuration of the stress measuring device can be made extremely simple and inexpensive.

Incidentally, the magnetized object 16 may deteriorate in its magnetized state with time or when a large load is applied. In this case, for example, the second object As in the embodiment, a coil for applying a DC magnetic field may be provided, and if necessary, a DC current may be applied to the coil to restore the magnetized state of the object 16 as needed. .

Next, a fifth embodiment of the stress measuring device of the present invention will be described with reference to FIG. FIG. 5 is a system configuration diagram showing a cross-sectional view of a part of the stress measuring device of the present embodiment.

The stress measuring device of this embodiment is configured as a load cell, and a rod 17 (object) made of a magnetostrictive body to which a load F is applied in the axial direction is erected on a pedestal 18 by a screw 18a. Installed and fixed. In this case, a vibration isolator 19 made of rubber or the like is interposed between the lower end surface of the rod 17 and the upper surface of the pedestal 18. Further, a vibration isolator 20 similar to the vibration isolator 19 is fixed to the lower surface of the pedestal 18, and the pedestal 18 is attached to the installation location of the stress measuring device via the vibration isolator 20.

A cylindrical magnetic shield member 21 made of pure iron or the like is externally inserted into the intermediate portion of
Holes 21a, 21b provided at the center of the upper end and the lower end of the magnetic shield member 21, respectively.
The upper end and the lower end of the rod 17 protrude from the rod 17 respectively.

Inside the magnetic shield member 21, annular magnets 22 and 23 concentrically externally mounted on the rod 17 are accommodated at the upper end portion and the lower end portion, respectively. , 23, a coil 25 inserted in a bakelite bobbin 24 is concentrically extrapolated to and accommodated in a rod 17, and these magnets 22, 23 and coil 2
5 has an outer peripheral surface fixed to an inner peripheral surface of the magnetic shield member 21 via a caulking material 26 in a vibration-proof manner. In this case, the magnets 22 and 23 are made of, for example, ferrite magnets, and apply a DC magnetic field to the axis of the rod 17 as indicated by an arrow H.

Further, a lead wire 27 for outputting the electromotive force signal from the coil 25 is led out of the magnetic shield member 21, and this lead wire 27 has the same configuration as the measuring circuit provided in each of the aforementioned embodiments. Is connected to the measuring circuit 5 of the first embodiment. The configuration of each part of the measurement circuit 5 is as described above, and the description is omitted here.

In the stress measuring device (load meter) of the present embodiment, when a load F that fluctuates with time acts on the upper end of the rod 17 in the axial direction of the rod 17, a stress corresponding to the load F is applied to the rod 17. At 17. And in this case,
The configuration of the stress measuring device of the present embodiment described above
Since the basic configuration is the same as that of the third embodiment (see FIG. 3), the time variation of the stress generated on the rod 17 by the coil 25 is exactly the same as that of the third embodiment. An electromotive force signal is generated. In other words, an electromotive force signal is generated in accordance with the amount of time change of the load F applied to the rod 17 and is output to the measurement circuit 5. Therefore, the signal obtained at the first output terminal 10 of the measurement and the like circuit 5 is the load F
The temporal variation of the load F can be accurately and stably measured based on the signal level.

The second circuit on the integrator 11 side of the measuring circuit 5
The signal obtained at the output terminal 12 indicates the magnitude of the load F, and the magnitude of the load F can be accurately and stably measured based on the signal level.

Next, a signal actually obtained by the stress measuring device of the present invention will be described with reference to FIG. 6, taking the fourth embodiment as an example.

The inventors of the present application can measure the temporal change of the stress generated in the object 16 by the electromotive force signal of the coil 4 in the stress measuring device of the fourth embodiment (see FIG. 4). In order to confirm that the magnitude of the stress can be measured by integrating the signal with the integrator 11, the following test was performed.

That is, the object 16 is magnetized in advance with a magnetic field of, for example, 25 Oe, and magnetized, and then a sine wave compression / tensile load as shown by a solid line a in FIG. It was applied in the axial direction of the object 16. Here, the applied compressive / tensile load is ± 300 kg (± 3 k
g / mm ² ) and a frequency of 20 Hz. Also,
The material of the object 16 is carbon steel.

At this time, the first output terminal 10 of the measuring circuit 5 is connected to the coil 4 as shown by the solid line b in FIG.
Was obtained. Further, a signal as shown by a solid line c in FIG. 6C was obtained at the second output terminal 12 which outputs a signal obtained by integrating the electromotive force signal by the integrator 11.

As shown in FIG. 6B, the electromotive force signal of the coil 4 is a sine wave, and the compressive / tensile load applied to the object 16 (the load proportional to the load causes a stress proportional to the load to be applied to the object 1).
6), which has a phase difference of 90 ° with respect to the sine wave. From this, it is understood that the electromotive force signal generated by the coil 4 at the time of applying the load described above indicates a temporal change amount (a time differential value of the stress) of the stress of the object 16 caused by the load.

Further, as shown in FIG.
The signal of the second output terminal 12 obtained by integrating the above electromotive force signal is a sine wave, and has the same phase as the sine wave of the compression / tensile load applied to the object 16. This indicates that a signal obtained by integrating the electromotive force signal of the coil 4 indicates the magnitude of the stress of the object 16.

Therefore, as described above, it is possible to directly measure the temporal change of the stress generated in the object 16 by the electromotive force signal of the coil 4, and to integrate the measured value into the object 16. It can be seen that the magnitude of the generated stress can be measured.

Although illustration and detailed description are omitted, the present inventors change the amplitude and frequency of the load applied to the object 16 to various sizes, and change the load applied to the object 16 to various sizes. The same test as described above was performed with a triangular wave shape. In each case, the same result as the above test was obtained.

In each of the embodiments described above, both the temporal change amount and the magnitude of the stress generated in the object when a load is applied are measured, but only one of them may be measured. The good thing is, of course.

Further, in each of the above-described embodiments, the method of measuring both the temporal change amount and the magnitude of the stress generated in the object by the signal of the single coil (flux change detecting means) has been described. Each coil may be provided to measure the temporal change and magnitude of the stress generated in each of the coils, and the temporal change and magnitude of the stress may be separately measured based on the signal of each coil.

Further, the stress measuring device of the present invention can
Not only can it be applied as the load cell described in the embodiment, it can also be applied to, for example, measuring the amount of time change or the magnitude of the stress generated in the vehicle or the like during a collision test or impact test of a vehicle or the like, Further, for example, in the case of an electronically controlled suspension of a vehicle, the magnitude of a load received by the suspension from a road surface and a temporal change amount are detected by using the stress measuring device of the present invention, and the damping force of a damper or the like of the suspension is controlled accordingly. Such a case can be applied.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a part of a first embodiment of a stress measuring device of the present invention in a perspective view.

FIG. 2 is a system configuration diagram showing a part of a second embodiment of the stress measuring device of the present invention in a perspective view.

FIG. 3 is a system configuration diagram showing a part of a third embodiment of the stress measuring device of the present invention in a perspective view.

FIG. 4 is a system configuration diagram showing a part of a fourth embodiment of the stress measuring device of the present invention in a perspective view.

FIG. 5 is a system configuration diagram showing a cross-sectional view of a part of a fifth embodiment of the stress measuring device of the present invention.

FIG. 6 is a diagram for explaining signal data actually obtained by the stress measuring device of FIG. 4;

[Explanation of symbols]

1, 16, 17: object, 2: magnetostrictive body, 3, 22, 23
... magnet (DC magnetic field applying means), 4,25 ... coil (magnetic flux change detecting means), 6,21 ... magnetic shield member, 13 ...
Coil (direct magnetic field applying means).

Claims (9)

[Claims] 1. A stress measuring device for measuring a temporal change of a stress generated in an object to which a load is applied, wherein the stress measuring device is fixed to the object and measures a change in magnetic permeability according to the stress generated in the object. A magnetostrictive body to be generated, DC magnetic field applying means for applying a DC magnetic field to the magnetostrictive body, and a time of a magnetic flux of the magnetostrictive body accompanying a change in magnetic permeability of the magnetostrictive body due to a stress generated in the object in a state where the DC magnetic field is applied. Magnetic flux change detecting means for generating a signal corresponding to the amount of change of the target, and the signal generated by the magnetic flux change detecting means indicates a temporal change of the stress generated in the object based on the signal. A stress measuring device for measuring a temporal change of a stress generated in an object. 2. A stress measuring device for measuring a temporal change of a stress generated in an object to which a load is applied, wherein the object is made of a magnetostrictive body which changes a magnetic permeability according to a stress generated in the object. DC magnetic field applying means for applying a DC magnetic field to the object, and a temporal change amount of a magnetic flux of the object due to a change in magnetic permeability of the object due to a stress generated in the object in a state where the DC magnetic field is applied. And a magnetic flux change detecting means for generating a signal corresponding to the signal.The signal generated by the magnetic flux change detecting means is generated in the object based on the signal as an indication of a temporal change amount of stress generated in the object. A stress measuring device for measuring a temporal change amount of a stress. 3. A stress measuring device for measuring the magnitude of stress generated in an object to which a load is applied, wherein the magnetostriction is fixed to the object and causes a change in magnetic permeability according to the stress generated in the object. Magnetic field applying means for applying a DC magnetic field to the magnetostrictive body, and a temporal change in magnetic flux of the magnetostrictive body accompanying a change in magnetic permeability of the magnetostrictive body due to a stress generated in the object in a state where the DC magnetic field is applied. A magnetic flux change detecting unit that generates a signal corresponding to the amount, and a signal generated by the magnetic flux change detecting unit is applied to the object indicated by the signal as indicating a temporal change amount of a stress generated in the object. An integrating means for integrating a temporal change amount of the generated stress, wherein a magnitude of the stress generated in the object is measured by an integrated value obtained by the integrating means. 4. A stress measuring device for measuring a magnitude of a stress generated in an object to which a load is applied, wherein the object is made of a magnetostrictive body which changes a magnetic permeability according to a stress generated in the object. DC magnetic field applying means for applying a DC magnetic field to an object, and according to a temporal change amount of a magnetic flux of the object due to a change in magnetic permeability of the object due to a stress generated in the object in a state where the DC magnetic field is applied. Magnetic flux change detecting means for generating a signal,
Integrating means for integrating the signal generated by the magnetic flux change detecting means as an indicator of the temporal change of the stress applied to the object, and integrating the temporal change of the stress applied to the object indicated by the signal; Wherein the magnitude of the stress generated in the object is measured based on the integrated value obtained by the integrating means. 5. The stress measuring device according to claim 1, wherein said DC magnetic field applying means is formed of a magnet or a coil to which a DC current is applied. 6. The stress measuring apparatus according to claim 1, wherein said DC magnetic field applying means is constituted by said object itself magnetized with a magnetic polarity in advance. 7. The measuring apparatus according to claim 1, wherein said magnetic flux change detecting means comprises a coil. 8. A stress measuring device according to claim 1, wherein a magnetic shield member is provided around said magnetostrictive body, DC magnetic field applying means and magnetic flux change detecting means. 9. The stress measuring device according to claim 2, wherein a magnetic shield member is provided around the object, the DC magnetic field applying means, and the magnetic flux change detecting means.